The bellcrank of a bucket linkage is pivotally mounted on the boom arms of a loader, with a bucket cylinder pinned between the loader frame and the upper arm of the bellcrank and a link pinned between the lower arm of the bellcrank and the bucket. This arrangement, which is commonly called a "Z-bar linkage", is highly advantageous because it permits use of a single bucket cylinder, provides an inherent self-leveling feature for the bucket as the boom arms are raised, provides high breakout force, and permits mounting the head end of the cylinder adjacent the frame to simplify routing of the hydraulic connections to the bucket cylinder. However, such an arrangement requires mounting the bellcrank between the boom arms which introduces stresses, particularly in bending, on the shaft mounting the boom arms and which requires accommodating or preventing changes in the distance between the boom arm as the boom arms are elastically deflected under load, especially during digging operations in which the loader is driven forward and the bucket is rotated into the material. In addition, the boom arms are positioned to pivot on the loader frame so that, when lowered, each boom arm passes between the frame and the adjacent tire.
In the prior art, a boss was formed on each boom arm and the shaft mounting the boom arm was secured to the boom arm by means of a bolt passing through aligned holes in the boss and the shaft. When the bosses are formed on the inside edge of each boom arm, the holes extending through the shaft are located in a high stress area and act as a stress riser, thereby having a detrimental effect on the operational life of the shaft. When the bosses are formed on the outside edge of each boom arm, the holes are positioned in a lower stress area, but the boss extending outward significantly reduces the clearance between the boss and the tire when the boom arms are lowered, thereby restricting the type of tire mounted on the loader wheels and/or eliminating the use of chains on the tires when operating in adverse terrain or ground conditions.
It is, therefore, an object to provide a bellcrank mounting for a loader linkage which has improved operational life, which does not adversely affect tire clearance, and which is relatively simple to manufacture and maintain.
It is also an object of this invention to provide a bellcrank mounting which avoids creating stress risers and which permits use of chains on the tires when desired.
It is a further object of this invention to provide a bellcrank mounting which securely anchors the bellcrank pivot shaft and which accommodates lateral deflections of the boom arms without detrimental effect on the mounting.